This invention relates to ferroelectrics devices such as ferroelectrics memories and ferroelectrics capacitors in which an extremely thin film of ferroelectrics excellent in crystalline characteristic is formed on a semiconductor substrate.
For instance U.S. Pat. No. 3,832,700 has proposed a FET (field-effect transistor) having an MFS (metal-ferroelectrics-semiconductor) structure as an application of the ferroelectrics device. Thereafter, use of ferroelectrics having a perovskite structure such as PZT (Pb (Zr, Ti) O.sub.3) has been tried for manufacture of the FET; however, it has not been realized due to a number of problems to be solved.
That is, the conventional ferroelectrics device is disadvantageous in the following points: In the device, the ferroelectrics is greatly mismatched (for instance in lattice constant) with the base material, namely, the semiconductor substrate, so that the formed ferroelectrics film is low in film quality. Furthermore, in manufacture of the ferroelectrics device, the components of the ferroelectrics are injected into the semiconductor, which makes it difficult to give excellent electrical characteristics to the ferroelectrics device. In addition, film formation and processing of the ferroelectrics material may damage the semiconductor substrate. This difficulty may be eliminated by provision of an intermediate layer (such as SiO.sub.2 or SiN). However, since it is low in dielectric constant, it is impossible to operate the ferroelectrics device without application of high voltage. Thus, in the case of the conventional ferroelectrics device, it is difficult to provide a thin film of ferroelectrics.